1D, 1-D, or 1d can refer to: Alpha-1D adrenergic receptor Astra 1D, a satellite Canon EOS-1D, Canon's first professional digital camera Long March 1D, a satellite One-dimensional space in physics and mathematics One Direction, an English-Irish boy band Penny (British pre-decimal coin), routinely abbreviated 1d. 1D, the hexadecimal code for the Group Separator control character Look up 1D, 1-D, or 1d in Wiktionary, the free dictionary. D1 (disambiguation) ID (disambiguation) LD (disambiguation) This disambiguation page lists articles associated with the same title formed as a letter–number combination.If an internal link led you here, you may wish to change the link to point directly to the intended article.